on an ink jet writing head, in particular for marking devices, with a ink chamber connected with an ink pressure source, wherein a plurality of closure elements, each closing an ink jet nozzle is located, each of said closure elements being connected with a tie rod, which moves out axially from the ink chamber and is connected with a driving device.
Ink jet writing heads of this type are used in particular as writing heads for marking devices, whereby lettering is applied to objects, for example packages, which are moved along the writing head. The ink jet nozzles of the writing head are arranged in a row tightly adjacent to each other and are actuated by the drive devices associated with each individual closure element by means of a control device, so that the lettering desired is applied to each passing object.
A design problem of ink jet writing heads of this type is due to the fact that the individual ink jet nozzles must be located with adequate tightness adjacent to each other, while the drive devices, usually electromagnets, have dimensions such that they cannot be placed as tightly together as the ink jet nozzles. For this reason, they are customarily arranged fanned out on either side of the plane containing the ink jet nozzles and their driving motion is transferred to the closure elements. This transfer may be effected by means of flexible wires, connected on one side with the closure element, and on the other with an actuating magnet (DE-OS 33 02 617). It is also known to connect each closure element with a tie rod, which at its end facing away from the closure element is joined to a tongue of the armature of an electromagnet.
As the ink in the ink chamber is under pressure, a pressure tight seal must be provided between the ink chamber and the tie rods or wires leading out of it. However, the friction generated in this seal impairs the operating safety of the ink jet writing head. On the one hand, undesirable wear is produced, while on the other, the seal friction interferes with the very rapid motion required of the closure elements.
It is therefore the object of the invention to develop an ink jet writing head of the aforementioned generic type in a manner such that it becomes possible to completely and effectively seal the tie rods leading out of the ink chamber without affecting the operation.